The NTSC-U demo and the one hidden in the game Spyro the Dragon show a few differences from the final version. Both demos are essentially the same, but the one in Spyro the Dragon is of a later build.

Note: These screenshots were taken using an emulator, so some fonts and textures look off-coloured.

Plane HUD

(contributed by Keiji Dragon and Crashpro)

This screenshot, taken from the trailer that precedes the playable level, shows how the plane HUD used to show an icon of Crash's plane, instead of a drawing of him wearing a pilot outfit. Since Coco wasn't originally intended to have her own plane, it's safe to assume an icon of her plane was never made.

The right side of the HUD shows a blimp icon instead of a red plane one. It oddly displays "0/0".

Time Twister

(contributed by Keiji Dragon)

An image of an early Time Twister can be seen as the texture for the warp sphere.

Gems

(contributed by Keiji Dragon)

The pause screen shows that there only used to be 40 gems in the game, instead of 42 (45 if you count the secret ones).

Relics

(contributed by Keiji Dragon and Zachcharge)

Sapphire relics underwent a few name and visual changes:

In the NTSC-U demo, they used to be called silver relics, with an appropriate white colour. They are still called that in the official Crash 3 site to this day.

In the later demo found in Spyro the Dragon, they're called Bronze Relics. This change was probably made because silver looked too much like platinum. They still look white in this demo, though. In the end, they ended up blue and renamed to sapphire.

Checkpoints and Jewels

Checkpoints and collectibles act the way they used to in Crash 2:

The checkpoints don't produce the usual fanfare when broken.

Getting a crystal or a gem doesn't produce the spark effect or play the heavenly choir.

Tell No Crates

(contributed by Keiji Dragon)

There used to be 60 crates in the level Tell No Tales instead of 61.

Line of Life

(contributed by Keiji Dragon)

In Tell No Tales, the line of 3 lives seen behind the yellow buoys in the final version appears about halfway through in the demo.

Crystal Placement

(contributed by Keiji Dragon)

The crystal in Tell No Tales is in a different place in the demo. It's suspended in mid-air, near the end.

Level List

(contributed by Werelion2367)

Some levels used to be swapped with each others by the time this demo was released. Additionally, some levels had different names altogether. Using GameShark, it's possible to see which ones were different:

Bone Yard was switched with Dino Might!

Makin' Waves was called Aye Matey.

Sphynxinator was called Sphynxter.

Future Frenzy was called Fast Forward.

Orange Asphalt was misspelled as Orange Asphault.

Flaming Passion was called Crash Kabob.

Some levels weren't yet named at all and went by these provisory names: